Inserter systems, such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. of Stamford, Conn.
In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation.
Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes.
The input stages of a typical inserter system are depicted in FIG. 1. At the input end of the inserter system, rolls or stacks of continuous printed documents, called a “web,” are fed into the inserter system by a web feeder 10. The continuous web must be separated into individual document pages. This separation is typically carried out by a web cutter 20 that cuts the continuous web into individual document pages. Downstream of the web cutter 20, a right angle turn 30 may be used to reorient the documents, and/or to meet the inserter user's floor space requirements.
The separated documents must subsequently be grouped into collations corresponding to the multi-page documents to be included in individual mail pieces. This gathering of related document pages occurs in the accumulator module 40 where individual pages are stacked on top of one another.
The control system for the inserter senses markings on the individual pages to determine what pages are to be collated together in the accumulator module 40. In a typical inserter application, mail pieces may include varying numbers of pages to be accumulated. For example, the phone bill for a person who lives by himself may be much shorter than another phone bill representing calls made by a large family. It is this variation in the number of pages to be accumulated that makes the output of the accumulator 40 asynchronous, that is, not necessarily occurring at regular time intervals.
Downstream of the accumulator 40, a folder 50 typically folds the accumulation of documents, so that they will fit in the desired envelopes. To allow the same inserter system to be used with different sized mailings, the folder 50 can typically be adjusted to make different sized folds on different sized paper. As a result, an inserter system must be capable of handling different lengths of accumulated and folded documents.
Downstream of the folder 50, a buffer transport 60 transports and stores accumulated and folded documents in series in preparation for transferring the documents to the synchronous inserter chassis 70.
In a typical embodiment of a prior art web cutter 20, the cutter is comprised of a guillotine blade that chops transverse sections of web into individual sheets. This guillotine arrangement requires that the web be stopped during the cutting process. As a result, the web cutter 20 transports the web in a sharp starting and stopping fashion and subjects the web to high accelerations and decelerations.
With the guillotine cutter arrangement, the web feeder 10 may typically include a loop control module to provide a loop of slack web to be fed into the web cutter 20. During high speed operation, the accelerations experienced by the web in the slack loop can be quite severe. The inertia experienced by the web from the sudden starting and stopping may cause it to tear or become damaged.
An alternative to the guillotine cutter arrangement is an arrangement using a rotary cutter. A rotary cutter utilizes a blade positioned transversely along a roller in a roller arrangement through which the web is transported. The rotary cutter module can simultaneously serve to continuously transport the web while cutting it into to predetermined length pieces as the blade on the roller comes into contact with the paper while the roller turns.
The rotary cutter arrangement does not include the disadvantage of sudden starting and stopping. However, a different disadvantage exists in that a rotary cutter requires a significant amount of time to decelerate when a downstream condition occurs that requires the system to stop. While the rotary cutter is decelerating to a stop, a number of additional sheets will be cut for which there may be no downstream space to accommodate.
A frequent limitation on speed of an inserter system is the ability of the system to handle all of the generated documents if the system is required to stop. An input system may be capable of going very fast under non-stop operating conditions, but a problem arises during stopping if there isn't a means to handle all the sheets produced by the input system. Thus in designing input stages to an inserter system, a consideration is to provide a place for all “work-in-progress” sheets and collations, assuming that the system may be required to stop at any time. A buffer module such as the ones described in co-pending patent applications Ser. No. 10/329,031 (issued as U.S. Pat. No. 6,687,570 on Feb. 3, 2004) and Ser. No. 10/328,971, (issued as U. S. Pat. No. 6,687,569 on Feb. 3, 2004), both filed on Dec. 24, 2002 and assigned to the assignee of the present application, may be used to provide stopping stations, or “parking spots,” for work-in-progress documents.
For proper operation, an inserter input system should not be run faster than spaces for holding work in progress can be made available. For mail runs including mail pieces having larger numbers of sheets, the problem is less severe since sheets from the same mail piece are stored together in the buffer stations. For mail runs with mail pieces only having a few sheets, the ratio of required stopping stations to the number of sheets generated will be greater, and the inserter input may be required to slow down.
The work-in-progress problem is amplified when a rotary cutter is used. Because of its greater inertia, a rotary cutter cannot be stopped as quickly as the guillotine style cutter. Thus, even more buffer capacity for handling and storing work in progress sheets must be included. Such additional capacity typically adds to the size and expense of the system.
One prior art solution to this disadvantage of rotary cutters has been to incorporate a vertical sheet stacking device downstream of the rotary cutter. Thus, any number of sheets cut from the rotary cutter could be piled into a vertical stack of individual sheets. Sheets may then be drawn from the bottom of the vertical stack as needed, and the problem of insufficient downstream space during a stopping condition is avoided. Such a vertical staking device is sometimes referred to as a “refeed device.”
Unfortunately, while solving one problem with rotary cutters, refeed devices cause another problem of their own. Refeed devices have been found to be insufficiently reliable for consistent feeding of cut sheets in the input subsystem of a high-speed inserter. For varying sheets sizes, paper weights, and curl conditions, a vertical stack feeding device has been found to incorrectly feed sheets from the bottom of the stack.